Flat and thin led-based luminary providing collimated light

Abstract

A light-emitting device ( 100 ), comprising a plurality of light emitting diodes ( 107 ) arranged spaced apart from each other on a substrate ( 108 ), is provided. The device further comprises a light guide plate ( 101 ) having a front surface ( 102 ) and an opposing back surface ( 103 ) that is provided with an array of protrusions ( 104 ) extending towards said substrate. The light guide plate is arranged such that light-emitting diodes emits light towards light receiving faces ( 105 ) of the protrusions ( 104 ). Further, collimators ( 110 ) are arranged between the light emitting diodes and the light receiving faces, to collimate the light before it enters the light guide plate. The light from the plurality of LEDs will be transmitted in to the light guide plate and will be distributed therein before exiting the light guide plate via the front side thereof. Thus, the present invention provides a light-emitting device that provides well-distributed and collimated light from a plurality of point light sources.

1 . Light emitting device, comprising:
 a plurality of light emitting diodes, spaced apart from each other on a substrate, said light emitting diodes being arranged to emit light in a general direction (L) along the surface of said substrate,   a light guide plate comprising a translucent material and having a back surface facing said substrate and an opposing front surface, said back surface comprising a first array of protrusions extending towards said substrate, said protrusions forming a light receiving face for transmitting light from the light emitting diodes into said light guide plate and a light reflection face for reflecting light in said light guide plate, and   a plurality of collimators arranged in the light path between said light emitting diodes and said first array of protrusions.   
     
     
         2 . A light emitting device according to  claim 1 , wherein said collimators collimate the light emitted by said light emitting diodes in a direction along the surface of said substrate and perpendicular to the general direction (L) of light emitted by said light emitting diodes. 
     
     
         3 . A light emitting device according to  claim 1 , wherein said collimators are funnel-shaped. 
     
     
         4 . A light emitting device according to  claim 1 , wherein a reflecting surface is arranged between said light guide plate and said plurality of collimators. 
     
     
         5 . A light emitting device according to  claim 1 , wherein a reflective surface is arranged between said substrate and said plurality of collimators. 
     
     
         6 - 7 . (canceled) 
     
     
         8 . A light emitting device according to  claim 1 , wherein said first array of protrusions comprises extended protrusions arranged substantially in parallel relative to each other. 
     
     
         9 . A light emitting device according to  claim 1 , wherein said protrusions of said first array have triangularly shaped cross-section. 
     
     
         10 . A light emitting device according to  claim 1 , wherein the angle (α) between said light receiving face and said front surface is larger than the angle (β) between said light reflecting face and said front surface. 
     
     
         11 . A light emitting device according to  claim 1 , wherein said substrate defines a plurality of spaced apart recesses. 
     
     
         12 . A light emitting device according to  claim 1 , wherein a redirection sheet is arranged at said front side of said light guide plate, said redirection sheet having a prism-faced surface facing said front side.